This invention relates to a transportation system in which a transport vehicle is moved relative to a structure for serving a plurality of spaced landings and includes a malfunction monitor for safely operating the vehicle.
Transportation systems, such as elevator systems, have been designed to move transport vehicles for carrying passengers and other items in both vertical and horizontal directions to serve a plurality of spaced landings. Elevator systems have been mounted to move a car or platform vertically along a guided path defined by guide rails or the like from one landing to another while subways, trains or the like have utilized rails to support and guide a vehicle for horizontal movement while other horizontally movable vehicles are supported by compressed air and restrained by guides for defined movement to travel in a path extending adjacent to landings for permitting passenger transfer at selected landings.
Many prior transportation systems have sensed one or more malfunctions to immediately stop the vehicle and prevent further operation. Such an immediate stoppage in an elevator system results in the vehicle being stalled in the shaft possibly between landings where the passengers would be stranded and isolated until the malfunction has been corrected. Some malfunctions require the attendance of service personnel frequently resulting in delays before the vehicle can be moved to an adjacent landing for passenger transfer.
Many transportation systems such as elevator systems have sensed a malfunction to operate a suicide circuit, such as in the U.S. Pat. No. 3,584,706 issued on June 15, 1971, which connects a generator armature to a generator shunt field thereby causing the armature current to flow in a manner to produce flux opposing any buildup in the generator while also setting a brake to immediately cease further vehicle movement. Such a system utilizes a generator to supply a variable voltage to an armature circuit of the hoist motor in which the shunt field of the generator is controlled to provide a speed control for the vehicle.
While it is sometimes desirable to immediately stop and stall a vehicle to prevent further movement to an adjacent landing for a serious malfunction occurring within the system, other less serious malfunctions might not require a total stoppage and stalling of the vehicle between transfer points particularly where the malfunction would not result in an extremely dangerous condition if continued vehicle movement were permitted under highly controlled and regulated conditions.
Some elevator type transportation systems have utilized auxiliary motors and/or auxiliary power sources which are selectively connected and operated in response to a sensed malfunction to move the vehicle to an adjacent landing to permit passenger transfer. Such additional motors and/or power sources require added and expensive equipment needing additional space for their presence. Such additional equipment can not be preferrably utilized with elevator systems which are constructed of modular prefabricated blocks because the uppermost modular penthouse block containing the motive equipment is frequently limited by size and weight requirements.
Many elevator type transportation systems require an attendant or serviceman to walk to the penthouse or other control area and manually energize a circuit from an auxiliary power source to lift the brake and permit the vehicle to travel to an adjacent landing after the vehicle has stopped and stalled within the shaft in response to a malfunction. Such systems frequently provide an auxiliary motor to facilitate the movement of the stalled vehicle which must also be manually operated from the penthouse or other control area.
Other elevator type transportation systems have permitted continued operation when sensing a malfunction by limiting or reducing the supply of energy to the elevator prime mover thereby operating the vehicle at a declining or reduced speed until reaching a landing at which a stop can be made. Such systems frequently energize the drive motor or prime mover by electric power supplied by a Ward-Leonard motor-generator control apparatus. One known system operates in response to a malfunction to let the rotor which energizes the generator to continue rotation through its inertia so that the generator continues to supply energizing voltage to the prime mover to move the vehicle to a landing in the direction in which the vehicle had been previously traveling. Another known elevator type transportation system operates in response to a malfunction and disconnects the energization of a first section of the shunt field of a generator supplying variable voltage to an armature of the hoist motor while continuing to energize the second section of the generator shunt field to continually supply driving power to the prime mover for continued travel, such as shown in U.S. Pat. No. 3,584,706. Such systems thus utilize a motor-generator type control apparatus widely utilized in many prior elevator type transportation systems which are difficult to utilize in modular type constructions because of their bulk and are relatively expensive units of the transportation system.
While many prior transportation systems have sensed malfunctions to modify their operation, the prior malfunction monitors together with the associated interconnected control systems would not be adaptable to a system in which a D.C. motor acting as the prime mover is coupled to receive energizing power directly from a static power converter which is utilized to transform an alternating current electrical input to a direct current electrical output used to energize and operate the motor. Because of the nature of such static power converters, a malfunction monitoring system must be able to quickly respond to varying operating conditions including transient conditions occurring within various stages of the power supply and control system to quickly modify the operation of the static power converter and other sequences and devices of the system.